Multi-branch stimulation electrode for subcutaneous field stimulation

ABSTRACT

A multi-branch stimulation electrode is disclosed herein. The multi-branch stimulation electrode can include a plurality of branches that extend from a hub. The branches can each include one or several stimulation contacts that can deliver an electrical current to tissue contacting the stimulation contacts. The stimulation contacts can be electrically connected with the lead. The lead can extend from the hub and can be connected with the pulse generator. The branches can include features to facilitate implantation including, for example, one or several removable stiffening elements.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/819,441, entitled “MULTI-BRANCH STIMULATION ELECTRODE FORSUBCUTANEOUS FIELD STIMULATION,” and filed on May 3, 2013, the entiretyof which is hereby incorporated by reference herein.

BACKGROUND

The prevalence of use of medical devices in treating ailments isincreasing with time. In many instances, and as these medical devicesare made smaller, these medical devices are frequently implanted withina patient. While the desirability of implantable devices is increasingas the size of the devices has decreased, the implantation process stillfrequently requires complicated surgery which can expose the patient tosignificant risks and protracted recovery times. In light of this,further methods, systems, and devices are desired to increase the easeof implantation of medical devices.

BRIEF SUMMARY

One aspect of the present disclosure relates to a neurostimulationsystem. The neurostimulation system includes an implantable pulsegenerator that can generate one or more non-ablative neurostimulationelectrical signals, and a multi-branch electrode array that can becoupled to the pulse generator to thereby transmit the one or morenon-ablative neurostimulation electrical signals to a nerve tissue. Themulti-branch electrode array can include a plurality of branches. Insome embodiments, at least some of the branches each include a pluralityof electrode contacts. In some embodiments, when in a deployedconfiguration, the plurality of branches diverge away from one anothersuch that distal tips of the branches are spaced farther apart thanproximate portions of the branches. In some embodiments, when in thedeployed configuration, the plurality of branches are in a substantiallyplanar arrangement.

In some embodiment of the neurostimulation system, the plurality ofbranches are in a rake-shaped arrangement when in the deployedconfiguration. In some embodiments, the substantially planar arrangementcomprises an arrangement in which the branches branch out across andcurve downwardly from a reference plane. In some embodiments, thedownward curve of the branches facilitates maintaining the branches in asubcutaneous tissue layer during deployment of the electrode array. Insome embodiments, at least some of the branches include blunt dissectingdistal tips.

In some embodiment of the neurostimulation system, the non-ablativeneurostimulation electrical signals have a pulse amplitude of 0-1,000mA. In some embodiments, the electrode array further can include a hubthat can include features to allow anchoring of the hub to a tissue. Insome embodiments, at least some of the electrode contacts are anodeelectrode contacts and wherein at least some of the electrode contactsare cathode electrode contacts. In some embodiments, of the electrodeson one branch are anode electrode contacts and all of the electrodes onan adjacent branch are cathode electrode contacts.

In some embodiment of the neurostimulation system, at least some of thebranches include stiffening components that increase the stiffness ofthe branches to facilitate blunt dissecting by the branches. In someembodiments, the stiffening components can be a plurality of elongatemembers that can be connected by a stiffening element hub. In someembodiments, at least some of the branches can receive the stiffeningelements.

In some embodiment of the neurostimulation system, the size of theelectrode contacts varies as a function of position on at least some ofthe branches. The branches have a proximal end and a distal end. In someembodiments, the size of the electrode contact increases when thedistance from the proximal end increases, or in other words, when theproximity of the electrode contact to the distal end of the branchincreases. In some embodiments, some of the electrode contacts are eachelectrically connected to a resistive element. In some embodiments, theresistance of the resistive element increases when the proximity of theelectrode contact to the proximal end of the branch increases.

One aspect of the present disclosure relates to an implantable electrodearray system. The implantable electrode array system includes amulti-branch electrode array including a plurality of elongated branchesthat each include at least one electrode contact and a blunt dissectingdistal tip, and an implantation cartridge for deploying the multi-branchelectrode array from a retracted configuration to a deployedconfiguration. In some embodiments, the branches are retracted relativeto the implantation cartridge when in the retracted configuration, and,wherein, the branches extend outwardly from the implantation cartridge afurther distance than in the retracted configuration when in thedeployed configuration. In some embodiments, the branches are arrangedin a substantially planar fan-shaped arrangement when in the deployedconfiguration.

In some embodiments, at least some of the branches include stiffeningcomponents that increase the stiffness of the branches to facilitateblunt dissecting by the branches. In some embodiments, the stiffeningcomponents can include a plurality of elongate members that areconnected by a stiffening element hub. In some embodiments, at leastsome of the branches can receive the stiffening elements. In someembodiments, the stiffening element can be a biodegradable outer layeron at least some of the branches. In some embodiment, at least some ofthe branches include an integrated stiffening element.

One aspect of the present disclosure relates to an implantable electrodearray. The implantable electrode array includes a multi-branch electrodearray including a plurality of elongated branches that each include atleast one electrode contact and a blunt dissecting distal tip. In someembodiments, the branches are arranged in a substantially planarfan-shaped arrangement when in the deployed configuration.

In some embodiments, at least some of the branches include stiffeningcomponents that increase the stiffness of the branches to facilitateblunt dissecting by the branches. In some embodiments, the stiffeningcomponents can be a plurality of elongate members that are connected bya stiffening element hub. In some embodiments, at least some of thebranches can receive the stiffening elements. In some embodiments, thestiffening element can be a biodegradable outer layer on at least someof the branches. In some embodiments, at least some of the branchesinclude an integrated stiffening element.

One aspect of the present disclosure relates to a method of implanting aneurostimulation system. The method includes pushing a plurality ofbranches of an electrode array into a subcutaneous tissue including orproximate nerve tissue such that distal tips of the plurality ofbranches pierce through the subcutaneous tissue and such that theplurality of branches fan outwardly into a substantially planarfan-shaped arrangement, and connecting the electrode array to aneurostimulation pulse generator that can stimulate the nerve tissue.

In some embodiments, the method can further include inserting animplantation cartridge through an incision. In some embodiments, theimplantation cartridge holds the plurality of branches of the electrodearray. In some embodiments, the method includes separating the pluralityof branches from the implantation cartridge and extracting theimplantation cartridge from the incision. The method can include,removing a stiffening element from at least one of the branches. In someembodiments, the method includes plugging any void left by the removingof the stiffening element from the at least one of the branches.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for purposes ofillustration only and are not intended to necessarily limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of an implantableneurostimulation system.

FIG. 2 is a top view of one embodiment of a multi-branch stimulationelectrode.

FIGS. 2A and 2B are side views of embodiments of the multi-branchstimulation electrode shown in FIG. 2.

FIG. 3 is a top view of one embodiment of an implantation systemincluding the multi-branch stimulation electrode.

FIGS. 4A-4C depict one embodiment of a process for implanting amulti-branch stimulation electrode.

FIG. 5 is a schematic illustration of one embodiment of a pulse deliverysystem.

FIG. 6 is a side view of one embodiment of a branch of a multi-branchstimulation electrode.

FIGS. 7A-7C are section views of embodiment of branches of amulti-branch stimulation electrode.

In the appended figures, similar components and/or features may have thesame reference label. Where the reference label is used in thespecification, the description is applicable to any one of the similarcomponents having the same reference label.

DETAILED DESCRIPTION OF THE FIGURES

A significant percentage of the Western (EU and US) population isaffected by Neuropathic pain (chronic intractable pain due to nervedamage). In many people, this pain is severe. There are thousands ofpatients that have chronic intractable pain involving a nerve.Neuropathic pain can be very difficult to treat with only half ofpatients achieving partial relief. Thus, determining the best treatmentfor individual patients remains challenging. Conventional treatmentsinclude certain antidepressants, anti-epileptic drugs and opioids.However, side effects from these drugs can be detrimental. In some ofthese cases, electrical stimulation, including FES, can provide effecttreatment of this pain without the drug-related side effects.

A spinal cord stimulator is a device used to deliver pulsed electricalsignals to the spinal cord to control chronic pain. Because electricalstimulation is a purely electrical treatment and does not cause sideeffects similar to those caused by drugs, an increasing number ofphysicians and patients favor the use of electrical stimulation overdrugs as a treatment for pain. The exact mechanisms of pain relief byspinal cord stimulation (SCS) are unknown. Early SCS trials were basedthe Gate Control Theory, which posits that pain is transmitted by twokinds of afferent nerve fibers. One is the larger myelinated Aδ fiber,which carries quick, intense-pain messages. The other is the smaller,unmyelinated “C” fiber, which transmits throbbing, chronic painmessages. A third type of nerve fiber, called Aβ, is “non-nociceptive,”meaning it does not transmit pain stimuli. The gate control theoryasserts that signals transmitted by the Aδ and C pain fibers can bethwarted by the activation/stimulation of the non-nociceptive Aβ fibersand thus inhibit an individual's perception of pain. Thus,neurostimulation provides pain relief by blocking the pain messagesbefore they reach the brain.

SCS is often used in the treatment of failed back surgery syndrome, achronic pain syndrome that has refractory pain due to ischemia. SCScomplications have been reported in a large portion, possibly 30% to40%, of all SCS patients. This increases the overall costs of patientpain management and decreases the efficacy of SCS. Common complicationsinclude: infection, hemorrhaging, injury of nerve tissue, placing deviceinto the wrong compartment, hardware malfunction, lead migration, leadbreakage, lead disconnection, lead erosion, pain at the implant site,generator overheating, and charger overheating. The occurrence rates ofcommon complications are surprisingly high: including lead extensionconnection issues, lead breakage, lead migration and infection.

Peripheral neuropathy, another condition that can be treated withelectrical stimulation, may be either inherited or acquired. Causes ofacquired peripheral neuropathy include physical injury (trauma) to anerve, viruses, tumors, toxins, autoimmune responses, nutritionaldeficiencies, alcoholism, diabetes, and vascular and metabolicdisorders. Acquired peripheral neuropathies are grouped into three broadcategories: those caused by systemic disease, those caused by trauma,and those caused by infections or autoimmune disorders affecting nervetissue. One example of an acquired peripheral neuropathy is trigeminalneuralgia, in which damage to the trigeminal nerve (the large nerve ofthe head and face) causes episodic attacks of excruciating,lightning-like pain on one side of the face.

A high percentage of patients with peripheral neuropathic pain do notbenefit from SCS for various reasons. However, many of these patientscan receive acceptable levels of pain relief via direct electricalstimulation to the corresponding peripheral nerves. This therapy iscalled peripheral nerve stimulation (PNS). As FDA approved PNS deviceshave not been commercially available in the US market, Standard spinalcord stimulator (SCS) devices are often used off label by painphysicians to treat this condition. A significant portion of SCS devicesthat have been sold may have been used off-label for PNS.

As current commercially-available SCS systems were designed forstimulating the spinal cord and not for peripheral nerve stimulation,there are more device complications associated with the use of SCSsystems for PNS than for SCS. Current SCS devices (generators) are largeand bulky. In the event that an SCS is used for PNS, the SCS generatoris typically implanted in the abdominal or in the lower back above thebuttocks and long leads are tunneled across multiple joints to reach thetarget peripheral nerves in the arms, legs or face. The excessivetunneling and the crossing of joints leads to increased post-surgicalpain and higher device failure rates. Additionally, rigid leads can leadto skin erosion and penetration, with lead failure rates being far toohigh within the first few years of implantation. Many or even mostcomplications result in replacement surgery and even multiplereplacement surgeries in some cases.

One embodiment of an implantable neurostimulation system 100 is shown inFIG. 1, which implantable neurostimulation system 100 can be, forexample, a peripherally-implantable neurostimulation system 100. In someembodiments, the implantable neurostimulation system 100 can be used intreating patients with, for example, chronic, severe, refractoryneuropathic pain originating from peripheral nerves. In someembodiments, the implantable neurostimulation system 100 can be used toeither stimulate a target peripheral nerve or the posterior epiduralspace of the spine.

The implantable neurostimulation system 100 can include one or severalpulse generators. The pulse generators can comprise a variety of shapesand sizes, and can be made from a variety of materials. In someembodiments, the one or several pulse generators can generate one orseveral non-ablative electrical pulses that are delivered to a nerve tocontrol pain. In some embodiments, these pulses can have a pulseamplitude of between 0-1,000 mA, 0-100 mA, 0-50 mA, 0-25 mA, and/or anyother or intermediate range of amplitudes. One or more of the pulsegenerators can include a processor and/or memory. In some embodiments,the processor can provide instructions to and receive information fromthe other components of the implantable neurostimulation system 100. Theprocessor can act according to stored instructions, which storedinstructions can be located in memory, associated with the processor,and/or in other components of the content injection system 100. Theprocessor can, in accordance with stored instructions, make decisions.The processor can comprise a microprocessor, such as a microprocessorfrom Intel® or Advanced Micro Devices, Inc.®, or the like.

In some embodiments, the stored instructions directing the operation ofthe processor may be implemented by hardware, software, scriptinglanguages, firmware, middleware, microcode, hardware descriptionlanguages, and/or any combination thereof. When implemented in software,firmware, middleware, scripting language, and/or microcode, the programcode or code segments to perform the necessary tasks may be stored in amachine readable medium such as a storage medium. A code segment ormachine-executable instruction may represent a procedure, a function, asubprogram, a program, a routine, a subroutine, a module, a softwarepackage, a script, a class, or any combination of instructions, datastructures, and/or program statements. A code segment may be coupled toanother code segment or a hardware circuit by passing and/or receivinginformation, data, arguments, parameters, and/or memory contents.Information, arguments, parameters, data, etc. may be passed, forwarded,or transmitted via any suitable means including memory sharing, messagepassing, token passing, network transmission, etc.

In some embodiments, the memory of one or both of the pulse generatorscan be the storage medium containing the stored instructions. The memorymay represent one or more memories for storing data, including read onlymemory (ROM), random access memory (RAM), magnetic RAM, core memory,magnetic disk storage mediums, optical storage mediums, flash memorydevices and/or other machine readable mediums for storing information.In some embodiments, the memory may be implemented within the processoror external to the processor. In some embodiments, the memory can be anytype of long term, short term, volatile, nonvolatile, or other storagemedium and is not to be limited to any particular type of memory ornumber of memories, or type of media upon which memory is stored. Insome embodiments, the memory can include, for example, one or both ofvolatile and nonvolatile memory. In one specific embodiment, the memorycan include a volatile portion such as RAM memory, and a nonvolatileportion such as flash memory.

In some embodiments, one of the pulse generators can be an externalpulse generator 102 or an implantable pulse generator 104. The externalpulse generator 102 can be used to evaluate the suitability of a patientfor treatment with the implantable neurostimulation system 100 and/orfor implantation of an implantable pulse generator 104.

In some embodiments, one of the pulse generators can be the implantablepulse generator 104, which can be sized and shaped, and made of materialto allow implantation of the implantable pulse generator 104 inside of abody. In some embodiments, the implantable pulse generator 104 can besized and shaped so as to allow placement of the implantable pulsegenerator 104 at any desired location in a body, and in someembodiments, placed proximate to a peripheral nerve such that leads(discussed below) are not tunneled across joints and/or such thatextension cables are not needed.

In some embodiments, the electrical pulses generated by the pulsegenerator can be delivered to one or several nerves 110 and/or to tissueproximate to one or several nerves 110 via one or several leads. Theleads can include conductive portions, such as electrodes or contactportions of electrodes, and non-conductive portions. The leads can havea variety of shapes, can be in a variety of sizes, and can be made froma variety of materials, which size, shape, and materials can be dictatedby the application or other factors.

In some embodiments, the leads can include an anodic lead 106 and/or acathodic lead 108. In some embodiments, the anodic lead 106 and thecathodic lead 108 can be identical leads, but can receive pulses ofdifferent polarity from the pulse generator.

In some embodiments, the leads can connect directly to the pulsegenerator, and in some embodiments, the leads can be connected to thepulse generator via a connector 112 and a connector cable 114. Theconnector 112 can comprise any device that is able to electricallyconnect the leads to the connector cable 114. Likewise, the connectorcable can be any device capable of transmitting distinct electricalpulses to the anodic lead 106 and the cathodic lead 108.

In some embodiments, the implantable neurostimulation system 100 caninclude a charger 116 that can be configured to recharge the implantablepulse generator 104 when the implantable pulse generator 104 isimplanted within a body. The charger 116 can comprise a variety ofshapes, sizes, and features, and can be made from a variety ofmaterials. Like the pulse generators 102, 104, the charger 116 caninclude a processor and/or memory having similar characteristics tothose discussed above. In some embodiments, the charger 116 can rechargethe implantable pulse generator 104 via an inductive coupling.

In some embodiments, one or several properties of the electrical pulsescan be controlled via a controller. In some embodiments, theseproperties can include, for example, the frequency, strength, pattern,duration, or other aspects of the timing and magnitude of the electricalpulses. In one embodiment, these properties can include, for example, avoltage, a current, or the like. In one embodiment, a first electricalpulse can have a first property and a second electrical pulse can have asecond property. This control of the electrical pulses can include thecreation of one or several electrical pulse programs, plans, orpatterns, and in some embodiments, this can include the selection of oneor several pre-existing electrical pulse programs, plans, or patterns.In the embodiment depicted in FIG. 1, the implantable neurostimulationsystem 100 includes a controller that is a clinician programmer 118. Theclinician programmer 118 can be used to create one or several pulseprograms, plans, or patterns and/or to select one or several of thecreated pulse programs, plans, or patterns. In some embodiments, theclinician programmer 118 can be used to program the operation of thepulse generators including, for example, one or both of the externalpulse generator 102 and the implantable pulse generator 104. Theclinician programmer 118 can comprise a computing device that canwiredly and/or wirelessly communicate with the pulse generators. In someembodiments, the clinician programmer 118 can be further configured toreceive information from the pulse generators indicative of theoperation and/or effectiveness of the pulse generators and the leads.

In some embodiments, the controller of the implantable neurostimulationsystem 100 can include a patient remote 120. The patient remote 120 cancomprise a computing device that can communicate with the pulsegenerators via a wired or wireless connection. The patient remote 120can be used to program the pulse generator, and in some embodiments, thepatient remote 120 can include one or several pulse generation programs,plans, or patterns created by the clinician programmer 118. In someembodiments, the patient remote 120 can be used to select one or severalof the pre-existing pulse generation programs, plans, or patterns and toselect, for example, the duration of the selected one of the one orseveral pulse generation programs, plans, or patterns.

Advantageously, the above outlined components of the implantableneurostimulation system 100 can be used to control and provide thegeneration of electrical pulses to mitigate patient pain.

With reference now to FIG. 2, a schematic illustration of one embodimentof a multi-branch stimulation electrode 200, also referred to herein asa multi-branch electrode array, is shown. In some embodiments, themulti-branch stimulation electrode 200 can be used in the place of oneor both of leads 106, 108 shown in FIG. 1. In some embodiments, themulti-branch stimulation electrode 200 can advantageously enabletreatment of a broader area than treated by use of leads 106, 108.Specifically, in some embodiments, the multi-branch stimulationelectrode 200 can enable peripheral field stimulation (PFS). In someembodiments, PFS includes the treatment of an area of pain or an area ofreferred pain. In some embodiments, this pain is not associated with anidentified nerve. In contrast to PNS in which a specific nerve isidentified and targeted, PFS can include stimulation of a broad area asno specific nerve is identified and targeted.

In one embodiment, for example, the broader area treatment enabled bythe multi-branch stimulation electrode 200 can ease placement of themulti-branch stimulation electrode 200 with respect to the nerve as theexact placement of the multi-branch stimulation electrode 200 is lessimportant than in the case of leads 106, 108. The multi-branchstimulation electrode 200 can, in some embodiments, be placed insubcutaneous tissue such as, for example, the layer of subcutaneousadipose tissue located between muscle and the epidermis.

The multi-branch stimulation electrode 200 can include a plurality ofbranches 202. In some embodiments, the branches 202 can be configured todeliver one or several electric pulses to tissue of the patient. In someembodiments, the branches 202 can comprise a variety of shapes and sizesand can be made from a variety of materials. In the embodiment depictedin FIG. 2, the branches 202 comprise a plurality of the elongate membersthat have a proximal end 204 and a distal end 206.

Multi-branch stimulation electrode 200 can have any desired number ofbranches including, for example, an even number of branches 202 or anodd number of branches 202. In some embodiments, the multi-branchstimulation electrode can have, for example, 2 branches 202, 3 branches202, 4 branches 202, 5 branches 202, 6 branches 202, 7 branches 202, 8branches 202, 9 branches 202, 10 branches 202, 11 branches 202, 12branches 202, 15 branches 202, 20 branches 202, 50 branches 202, and/orany other or intermediate number of branches. In some embodiments, someof the branches 202 can be an anodic branches, and some of the branches202 can be cathodic branches. In some embodiments, the branches 202 canalternate between anodic and cathodic branches such that the adjacentbranches 202 to an anodic branch are cathodic branches and the adjacentbranches to a cathodic branch are anodic branches. Alternatively, insome embodiments, some or all of the branches can include one or severalstimulation contacts that can be anodic stimulation contacts, and someor all of the branches can include one or several stimulation contactsthat can be cathodic stimulation contacts. In some embodiments, thesestimulation contacts can alternate such that an anodic stimulationcontact is adjacent to cathodic stimulation contacts, and such thatcathodic stimulation contacts are adjacent to anodic stimulationcontacts. Advantageously, by alternating between an anodic and acathodic branch, and/or alternating between anodic and cathodicstimulation contacts, the creation of circuits through the patient'stissue to allow transmission of electric pulses can be facilitated. Insome instances, the system is designed to re-configure one or more ofthe branches between anodic or cathodic configurations and/or one ormore of the stimulation contacts between anodic or cathodicconfigurations.

In some embodiments, each of the branches 202 can be the same size, havethe same shape, and be made from the same material, and in someembodiments, some of the branches 202 can have one of a different size,shape, or material than others of the branches 202. For example, in theembodiment depicted in FIG. 2, a first branch 202-A, located along acentral axis of the multi-branch stimulation electrode 200, is longerthan a second branch 202-B, located adjacent to the central access ofthe multi-branch stimulation electrode 200. In the embodiment depictedin FIG. 2, the first branch 202-A extends parallel to a y-axis such thatthe distal end 206 is farther in the positive y-direction than theproximal end 204. As further seen in FIG. 2, the first branch 202-Aextends perpendicular to the x-axis, and the second branch 202-B isfarther in the positive x-direction than the first branch 202-A.Although not shown, the multi-branch stimulation electrode 200 can befurther defined by the z-axis which extends from the intersection of thex- and y-axes according to the right-hand rule.

In the embodiment depicted in FIG. 2, the branches 202 can be spacedapart from each other. In some embodiments, the branches 202 can bespaced apart from each other such that branches 202 extend parallel toeach other, and in some embodiments, the branches can be spaced apartsuch that the branches 202 are non-parallel to each other. As describedfurther below, in some instances, the spacing and arrangement of thebranches will vary depending on whether the electrode array is in adeployed or non-deployed configuration. In some embodiments, thebranches 202 can be spaced in a fan or rake-shaped arrangement, whereinthe proximal ends 204 of the branches 202 are spaced more closely toeach other than are the distal ends 206 of the branches. In someembodiments, the nonparallel extension of the branches 202 (when in adeployed configuration) can result in changing spacing between thebranches. Specifically, in the embodiment depicted in FIG. 2, thespacing between the branches 202 increases when moving in the positivey-direction (towards the top of the page) from the proximal end 204 tothe distal end 206 of any of the branches 202. In some embodiments, someor all of the branches 202 can be each located in a single plane alongthe z-axis (e.g. in a plane defined by or parallel to the page of FIG.2) and in some embodiments, one or several of the branches 202 can belocated in multiple planes along the z-axis, and/or extend throughmultiple planes along the z-axis. In some embodiments, the position ofthe branches 202 along the z-axis can serve to match the shape of themulti-branch stimulation electrode 202, for example, a curved body partinto which the multi-branch stimulation electrode 202 is beingimplanted. In one embodiment in which the multi-branch stimulationelectrode 202 is configured for being implanted in, for example, a limb,the position of a point on one or several of the branches 202 in thez-axis can vary as a function of, for example position on the y-axisand/or on the x-axis. In some embodiments, the shaping of themulti-branch stimulation electrode 202 in the z-axis can facilitatemaintaining the multi-branch stimulation electrode 200 in thesubcutaneous tissue. In one embodiment, for example, the position of apoint on one or several of the branches 202 z-axis can vary as afunction of distance in the x-axis from the first branch 202-A.

In the particular embodiment of FIG. 2, the branches 202 of theelectrode array are in a substantially planar arrangement, although thebranches 202 are not entirely located in a single plane. As shown inFIG. 2A, which shows the electrode array of FIG. 2 in a side view, allof the branches 202 curve slightly downwardly towards distal tips of thebranches 202, which facilitates maintaining the branches 202 in asubcutaneous layer of tissue during implantation and insertion, asdescribed further below. As shown in FIG. 2B, which shows anotherembodiment of the electrode array of FIG. 2 in a side view, some of thebranches 202 curve slightly downwardly towards distal tips of thebranches 202, which facilitates maintaining the branches 202 in asubcutaneous layer of tissue during implantation and insertion, asdescribed further below. In some embodiments, the branches 202 curvedownwardly such that the distal tips are approximately 0.5 mm, 1 mm, 2mm, 3 mm, 5 mm, 10 mm, 15 mm, and/or any other or intermediate distancebelow proximal ends of the branches.

As the spacing between the branches 202 changes, the spacing between theconductive portions of the branches 202, which may be stimulationcontacts or electrode contacts, changes. This change in the distancebetween the conductive portions of the branches 202 changes one orseveral of the electrical properties, which can be, for example,impedance, of the circuit extending from one of the conductive portionsof one branch to another conductive portion of another branch. In someembodiments, differences in electrical properties of circuits extendingfrom different conductive portions of different branches to each otheraffects the ability of the implantable neurostimulation system 100 toprovide desired stimulation to a nerve and/or area.

In some embodiments, for example, in which the electrical property is animpedance, different impedances for different circuits can result inmore current passing through some circuits and less current passingthrough others. This can disadvantageously result in unequal stimulationacross an area and of a nerve which can inhibit the ability of theimplantable neurostimulation system 100 to treat pain and/or tostimulate a nerve. In some embodiments, the multi-branch stimulationelectrode 200 can include one or several features configured tocounteract the effects of differential spacing between conductiveportions of different branches such that the electrical properties ofthese circuits are the same and/or approximately the same. In someembodiments, the electrical properties of the circuits are approximatelythe same when they vary by less than 40%, 30%, 20%, 10%, 5%, 1%, or anyother or intermediate percent from each other.

In some embodiments, some or all of the branches 202 can include a body208. The body 208 can comprise a variety of shapes and sizes and can bemade from a variety of materials. In some embodiments, the body 208 canextend the entire length of the branch 202, and in some embodiments, thebody can extend a portion of the length of the branch 202. In someembodiments, the body 208 can be approximately cylindrical when the body208 is positioned to extend in a straight line and body 208 can have acircular cross-section.

In some embodiments, the body 208 can be rigid, flexible, and/orelastic. In some embodiments, the properties of the body 208 canfacilitate the implantation of the body 208 and decrease problems causedby the implantation of the body 208. In some embodiments, the body 208can be more easily implanted when it is rigid. In some embodiments, thebody 208 is less likely to cause negative side effects when the body 208is flexible and/or elastic. In some embodiments, the body 208 can bemade of a material that is rigid at a first, pre-insertion temperatureand flexible at a second, body temperature. In some embodiments, suchmaterial can be rigid during the implantation process but can, as thebody 208 warms to body temperature, become flexible. In such anembodiment, the body can have an “integrated stiffening element.”Properties of some aspects of stiffening elements will be discussed atgreater lengths below. In some embodiments, the body 208 can include,for example, a rigid, biodegradable outer coating and a flexible, innerportion. In such an embodiment, the rigid, biodegradable outer coatingcan biodegrade after the implantation of the body 208 to leave theflexible, inner portion of the body 208. In some embodiments, the body208 can comprise a flexible member and a stiffening member, which canbe, for example, a pre-formed stiffening member, can be inserted intothe body 208 to facilitate implantation. In such an embodiment, afterthe body 208 has been implanted, the stiffening member can be removed.

In some embodiments, the bodies 208 of the branches 202 can comprise abiocompatible material. In some embodiments, the bodies 208 of thebranches 202 can comprise, for example, a natural material, a man-madematerial, a polymer, a metal or metal alloy, or the like. In someembodiments, the material of the body 208 can be selected so as to beflexible at a body temperature and to be rigid or semi rigid at roomtemperature.

In some embodiments, some or all of the branches 202 can include one orseveral stimulation contacts 210 that can be, for example, located atpositions along the body 208 of the therewith associated branch 202. Theone or several stimulation contacts 210 can be configured to pass one orseveral electrical pulses to a portion of the patient's tissue. In someembodiments, the stimulation contacts 210 can comprise a conductivematerial that can form, for example, a peripheral band around one orseveral portions of the body 208. In some embodiments, the stimulationcontacts 206 can radially extend beyond the outside edge of the body 204so as not to be flush with the body 204, and in some embodiments, thestimulation contacts 206 can be flush with the body 204.

The stimulation contacts 210 on a single branch 202 can be spaced apart.In some embodiments, each of the stimulation contacts 210 can be equallyspaced along the body 208 of the branch 202, and in some embodiments,the stimulation contacts 210 can be unequally spaced and/or unevenlyspaced along the body 208 of the branch 202.

The stimulation contacts 210 can comprise a variety of shapes and sizesand can be made from a variety of materials. In some embodiments, eachof the stimulation contacts 210 can comprise the same size and/or shape,and in some embodiments, some or all of the stimulation contacts 210 cancomprise different sizes and/or shapes. In some embodiments, the size,shape, and/or material of some or all of the stimulation contacts 210can be selected based on desired effect on one or several electricalproperties of the completed circuit including to stimulation contacts210 and a portion of the patient tissue. In one embodiment, for example,the size of the stimulation contacts 210 can increase as the distance ofthe stimulation contact 210 from the proximal end 204 of the branchincreases.

In some embodiments, the stimulation contacts 210 can have similarand/or the same material properties as the material of the body 208.Advantageously the matching and/or pairing of the material properties ofthe stimulation contacts 210 and the body 208 can decrease stresses thatmay arise in the one or both of the body 208 and the stimulationcontacts 210 during implantation of the multi-branch stimulationelectrode 200 in the body of a patient.

In some embodiments, and as seen in FIG. 2, the proximal ends 204 of thebranches 202 connect to hub 212. The hub 212 can comprise a variety ofshapes and sizes and can be made from a variety of materials. In someembodiments, the hub 212 can comprise a biocompatible outer housingand/or can be made up one or several biocompatible materials. In someembodiments, the housing of the hub 212 can comprise an interior housingand/or an exterior housing. In some embodiments, the interior housing ofthe hub 212 can be rigid and the exterior of the hub 212 can be flexibleand/or deformable. Advantageously, a flexible and/or deformable exteriorhousing of the hub 212 can decrease irritation that may arise fromimplanting the hub 212 in the patient's body.

The branches 202 can connect to the hub 212 in many ways. In someembodiments, the connections of the branches 202 to the hub 212 can bewithin a single plane in the Z axis, and in some embodiments, theconnections of the branches 202 to the hub 212 can be in multiple planesin the z-axis. In some embodiments, the connections of the branches 202to the hub 212 can be spaced along the x-axis and can, for example, beequally spaced along the x-axis. In some embodiments, the hub 212,including the connection points of the branches 202 to the hub 212, canbe sealed so as to decrease the likelihood of bacterial growth withinand/or associated with the hub 212.

The hub 212 can include one or several anchor features 214 that can beused to secure and/or fix the position of the hub 212 in the patient'sbody. In the embodiment depicted in FIG. 2, these anchor features 214comprise suture eyelets that can be used in suturing the hub to tissuewithin the patient's body.

The hub 212 can connect to lead 216, which lead 216 can connect to oneof the pulse generators 102, 104. Hub 212 can include one or severalconductors that are electrically connected with one or several of thestimulation contacts 210 of the branches 202. These one or severalconductors can be used to conduct electrical pulses from the pulsegenerator 102, 104 to the stimulation contacts 210. In some embodiments,the one or several conductors can be enclosed in an insulative,biocompatible shell. In some embodiments, the conductors and thebiocompatible shell can be flexible and/or rigid, can comprise a varietyof shapes and sizes, and can be made from a variety of materials.

With reference now to FIG. 3, a schematic illustration of one embodimentof an implantation system 300 is shown. In some embodiments, theimplantation system 300 can be used to implant the multi-branchstimulation electrode 200 in a patient's body. The components of theimplantation system 300 can comprise a variety of shapes and sizes andcan be made from a variety of materials. In some embodiments, thecomponents of the implantation system 300 and the implantation system300 as a whole can be sized and shaped to allow insertion of portions ofthe implantation system 300 through an incision 302. As seen in FIG. 3,the implantation system includes the multi-branch stimulation electrode200 including, the leads 202, and the hub 212.

The implantation system 300 can include an implantation cartridge 304that can include an insertion tip 305. The insertion tips 305, alsoreferred to herein as a piercing tip, can be configured to pierce tissueof the patient. The implantation cartridge 304 can comprise a variety ofshapes and sizes and can be made of a variety of materials. In someembodiments, for example, the insertion tip 305 of the implantationcartridge 304 can extend to a point where a rounded tip and/or can taperto a point or a rounded tip. In some embodiments, the point or roundedtip can be inserted into the patient's body through the incision 302 andcan ease the insertion of the implantation cartridge 304 through theincision 302.

In some embodiments, the implantation cartridge 304 can comprise anelongate member having a U-shaped cross-section with a bottom and sidesextending in the same direction from the bottom. This bottom and sidesof the implantation cartridge 304 partially bound an internal volume ofthe implantation cartridge 304. In some embodiments, the othercomponents of the implantation system 300 can be held within and/orretained within the internal volume of the implantation cartridge 304.

In some embodiments, the implantation cartridge 304 can be configured tohouse the multi-branch stimulation electrode 200 and hold the branches202 of the multi-branch stimulation electrode 200 in a first, insertionposition. As depicted in FIG. 3, the branches 202, which can be, forexample, pre-formed branches of the multi-branch stimulation electrode200 that are held parallel to each other in the first, insertionposition. The implantation cartridge 304 can include features configuredto hold the branches 202 of the multi-branch stimulation electrode 200and the first, insertion position. In one embodiment, for example, thefeatures configured to hold the branches 202 of multi-branch stimulationelectrode 200 in the first, insertion position can comprise acomb-shaped guide. In one such embodiment, one or several of thebranches 202 of the multi-branch stimulation electrode 200 can be heldbetween teeth of the comb-shaped guide. In such an embodiment, the teethof the comb shaped guide can extend in the same direction as the sidessuch that the comb shaped guide and the implantation cartridge 304 canbe lifted off of the multi-branch stimulation electrode 200 afterimplantation of the multi-branch stimulation electrode 200 in thepatient's body.

The implantation system 300 can include an insertion sleigh 306. In someembodiments, the insertion sleigh can fit within the internal volume ofthe implantation cartridge 304 and can be slidable towards and away fromthe insertion tip 305 of the implantation cartridge 304. In someembodiments, the insertion sleigh 304 can engage with, for example, someor all of the multi-branch stimulation electrode 200 such as, forexample, the hub 212 to allow insertion of and/or implantation of themulti-branch stimulation electrode 200 when the insertion sleigh 304 ismoved towards the insertion tip 305 of the implantation cartridge 304.

With reference now to FIGS. 4A, 4B, and 4C a schematic illustration ofone embodiment of a process for the implantation of the multi-branchstimulation electrode 200 is shown. The process begins in FIG. 4A,wherein the insertion tip 305 of the insertion cartridge 304 is insertedthrough the incision 302 in the patient's body.

After the insertion cartridge 304 is placed in the desired position, theinsertion sleigh 306 is displaced towards the insertion tip 305 of theinsertion cartridge 304. As the insertion sleigh 306 is displacedtowards the insertion tip 305 of the insertion cartridge 304, thebranches 202 of the multi-branch stimulation electrode 200 penetrateinto the tissue of the patient and move towards a second, implantedposition. In some embodiments, the branches 202 of the multi-branchstimulation electrode 200 have a desired spacing and distribution whenthey reach the second, implanted position.

FIG. 4B depicts one embodiment of the implantation system 300 after thebranches 202 of the multi-branch stimulation electrode 200 have reachedthe second, implanted position. As seen, the branches 202 of themulti-branch stimulation electrode 200 have reached the second,implanted position when the insertion sleigh 306 has reached theinsertion 305 of the insertion cartridge 304 and when the hub 212 of themulti-branch stimulation electrode is inserted through the incision 302.

After the branches 202 of the multi-branch stimulation electrode 200have reached the second, implanted position, and after the multi-branchstimulation electrode 200, including the branches 202 have reached adesired position, the insertion sleigh 306 and the insertion cartridge304 are separated from the multi-branch stimulation electrode andremoved from the patient's body out of the insertion 302 as is depictedin FIG. 4C. In some embodiments, after the separation of themulti-branch stimulation electrode 200 from the insertion sleigh 306 andthe insertion cartridge 304, the multi-branch stimulation electrode 200can be secured with respect to the incision 302 and/or with respect tothe patient's body. In some embodiments, the multi-branch stimulationelectrode 200 can be secured with respect to the patient's body via theanchor features 214 of the hub 212.

After the multi-branch stimulation electrode has been secured within thepatient's body, and as further depicted in FIG. 4C, the stiffeningelements 308, if the multi-branch stimulation electrode 200 includesstiffening elements 308, can be withdrawn. In some embodiments, thestiffening elements 308 can provide rigidity to the branches 202 of themulti-branch stimulation electrode 200 to allow penetration of thebranches 202 into and through tissue of the patient's body, and in someembodiments, the stiffening elements 308 can bias the branches 202 ofthe multi-branch stimulation electrode 200 towards the second, implantedposition. After the branches 202 have reached the desired position, thestiffening elements 308 can be withdrawn from the branches 202 so thebranches 202 have a desired level of flexibility. In some embodiments,the stiffening members 308 can be connected to a stiffening element hub310 and the stiffening members 308 can be withdrawn from the branches202 of multi-branch stimulation electrode 200 by withdrawing thestiffening element hub 310 from the hub 212 and out of and through theincision 302. In the event that the withdrawal of the stiffening members308 created one or several voids or cavities within one or both of thehub 212 and the branches 202, the one or several voids or cavities canbe sealed, plugged, and/or filled.

With reference now to FIG. 5, a schematic illustration of one embodimentof a pulse delivery system 500 is shown. The pulse delivery system 500can include the implanted multi-branch stimulation electrode 200including, for example, branches 202 in the second, implanted positionand hub 212. In some embodiments, and as shown in FIG. 5, the lead 216of the multi-branch stimulation electrode 200 can be connected to thepulse generator 102, 104. In some embodiments, the hub 212 and thebranches 202 of the multi-branch stimulation electrode 200 can beimplanted within the patient's body, inserted past the incision 302, andthe lead 216 can extend through the incision 302 from inside thepatient's body to outside the patient's body. The lead 216 and canconnect to the pulse generator 102, 104 at a point outside the patient'sbody. However, in other embodiments, the lead 216 can be entirelyimplanted within the patient's body and the pulse generator 102, 104 canlikewise be entirely implanted within the patient's body.

With reference now to FIG. 6, a side view of one embodiment of one ofthe branches 202 is shown. The branch 202 can include the proximal end204 connecting to the hub 212 that contacts the stiffening member hub312, and the distal end 206. As depicted in FIG. 6, the distal end 206of the branch 202 can include the insertion member 400. The insertion ofthe 400 can comprise a variety of shapes and sizes and can be made froma variety of materials. In some embodiments, the insertion member 400can be configured to interact with the stiffening member 308 during theimplantation of the hub 212 to prevent the stiffening member 308 frompenetrating through the branch 202. In such embodiments, the insertionmember 400 can comprise a penetration material that can be, for example,metal, hard plastic, a composite, and/or any other material capable ofinteracting with the stiffening member 308 during the implantation andnot allowing the stiffening member to penetrate the branch 202. In someembodiments, the insertion member 400 can be further configured tofacilitate implantation. In such embodiments, the insertion member 400can be shaped to facilitate the insertion and can include, for example,a pointed tip.

The branch 202 depicted in FIG. 6 further includes an elastic zone 402and an inelastic zone 404. The elastic zone 402 can be a portion of thebranch 202 that has elastic properties and therefore allows a dimensionof the branch 202 to temporarily change in response to the applicationof a force. In some embodiments, the elastic zone 402 can be located atany position on and/or along the insertion member 202 and the elasticzone 402 can have any desired size and shape.

In some embodiments, the entire branch 202 can be the elastic zone 402,and in some embodiments, the branch 202 can include an inelastic zone404. The inelastic zone can be a portion of the branch 202 that is notintended to have elastic properties and/or that does not have elasticproperties at the load levels applied during the implantation of themulti-branch stimulation electrode 200. In some embodiments, the elasticzone 402 can be located proximate to the proximal end 204 of the branch202 and the inelastic zone 404 can be located proximate to the distalend 206 of the branch 202. In some embodiments, and as depicted in FIG.6, the stimulation contacts 210 can be located in the inelastic zone404. Advantageously, placement of the stimulation contacts 210 in theinelastic zone can decrease stresses created in one or both of thestimulation contacts 210 and the branch 202 during the implantation ofthe multi-branch stimulation electrode 200 by eliminating and/ordecreasing discrepancies between the material properties of thestimulation contacts 210 and the branch 202.

With reference now to FIG. 7A-7C, section views of some embodiments ofthe branch 202 are shown. With reference now to FIG. 7A, section view ofone embodiment of branch 202 is shown. The branch 202 is connected atits proximal end 204 to hub 212, which hub is connected to lead 216 andcontacts stiffening element hub 312. The branch 202 further includes apenetrating element 400 located at the distal end 200. In someembodiments, the branch 202 can include one or several branch walls 406that can define an internal channel 408 of the branch 202. In someembodiments, the internal channel 408 can comprise a single channel thatcan be, for example, configured to receive a stiffening element 308, andin some embodiments, the internal channel 408 can comprise a channelconfigured to receive the stiffening element 308 and a channelconfigured to receive one or several conductors configured to connectthe stimulation contacts 210 to the lead 216.

In some embodiments, the one or several conductors can be incorporatedinto the branch walls 406 of the branch 202, and in some embodiments,the one or several conductors can be loosely contained within theinternal channel 408. In the embodiment depicted in FIG. 7A, the branch202 includes a single internal channel 408 configured to receive boththe stiffening element 308, a main wire 410, and a plurality of branchwires 412. In some embodiments, the main wire 410 can carry electricalpulses from the lead 216 to the stimulation contacts 210. In someembodiments, the main wire can connect to the lead 216 in the hub 212and can be electrically connected to the stimulation contacts 210 viaone or several branch wires 412. In some embodiments, the branch wirescan include one or several electrical components configured to carryelectrical property of the circuit with which the stimulation contact210 connected to the branch wire 412 is associated. In some embodiments,these electrical components can include one or several resistors,capacitors, or the like.

As further seen in FIG. 7A, in some embodiments, the stiffening element308 can extend from the stiffening element hub 312 to contact theinsertion tip 400. In some embodiments, as slight differences in thelength of one or several of the branches 202 and/or of the stiffeningelements 308 may arise, the stiffening elements 308 may not adequatelystiffen one or several of the branches 202 to allow implantation of thebranches 202.

In one embodiment, for example, one of the stiffening elements 308 maybe relatively longer than others of the stiffening elements 308 withrespect to one or several branches. As such, the relatively longer ofthe stiffening elements 308 may contact the insertion tip 408 of one ofthe branches 202 and others of the stiffening elements 308 may notcontact the insertion tip 408 of the others of the branches 202.

In some embodiments, the multi-branch stimulation electrode 200 caninclude one or several features to overcome these problems to therebyfacilitate implantation of multi-branch stimulation electrode 200. Insome embodiments, these features can include one or several elasticportions of the branches 202. In some embodiments, these features caninclude one or several features located in the stiffening element 308and/or in the stiffening element hub 312 that can allow a change to thelength of the stiffening element and/or similar features in the hub 212which can allow changes in the length of the branches 202.Advantageously, such features can allow for improved implantation of themulti-branch stimulation electrode 200.

With reference now to FIG. 7B, a section view of one embodiment of abranch 202 is shown. In this embodiment, the branch 202 includesfeatures configured to facilitate in creating the same and/or similarelectrical properties at circuits arising when the branches 202 of themulti-branch stimulation electrode 200 are not parallel spaced, andfeatures configured to allow the branch 202 to stretch so as tocompensate for discrepancies in the length of some or all of thebranches 202 and/or the stiffening elements 308. As specifically seen,in the embodiment depicted in FIG. 7B, the branch 202 includes extendingwire 414 and returning wire 416. The extending wire extends from the hub212 towards the distal end 206 of the branch 202 wherein the directionof the extension of the wire changes and the returning wire 414 returnstowards the hub 212. In some embodiments, this can reverse the orderwith which the stimulation contacts 210 are connected to the wire whichcan thereby result in the greatest amount of resistance beingexperienced at the stimulation contact 210 relatively closest to the hub212. In some embodiments, this looping of the wire can further provideaccess wire within the branch 202 such that the wire does not break orstretch if the branch 202 elastically deforms during implantation of themulti-branch stimulation electrode 200.

With reference now to FIG. 7C, a section view of one embodiment of thebranch 202 is shown. In this embodiment, the branch 202 includesfeatures configured to allow the branch 202 to stretch so as tocompensate for discrepancies in the length of some or all of thebranches 202 and/or the stiffening elements 308. As specifically seen,the main wire 410 includes a plurality of extension coils 418 located inthe internal channel 408 of the branch 202. In some embodiments, theseextension coils 418 can allow the overall length of the main wire 410 tochange with changes in the length of the branch 202. Advantageously,this can allow for the elastic deformation of the branch 202 withoutstretching and/or breaking the main wire 410. The extension coils cancomprise a variety of shapes and sizes and can include, for example, anydesired number of loops or coils. In some embodiments, the extensioncoils 418 can be designed according to expected changes in the length ofthe branch 202.

In the foregoing specification, the invention is described withreference to specific embodiments thereof, but those skilled in the artwill recognize that the invention is not limited thereto. Variousfeatures and aspects of the above-described invention can be usedindividually or jointly. Further, the invention can be utilized in anynumber of environments and applications beyond those described hereinwithout departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive. It will be recognizedthat the terms “comprising,” “including,” and “having,” as used herein,are specifically intended to be read as open-ended terms of art.

What is claimed is:
 1. A neurostimulation system, comprising: (a) animplantable neurostimulation pulse generator configured to generate oneor more neurostimulation electrical signals; (b) a multi-branchelectrode array configured to be coupled to the pulse generator and totransmit the one or more non-ablative neurostimulation electricalsignals to a nerve tissue, the multi-branch electrode array comprising:(i) a plurality of branches, wherein at least some of the branches eachinclude a plurality of electrode contacts; (ii) wherein, when in adeployed configuration, the plurality of branches diverge away from oneanother such that distal tips of the branches are spaced farther apartthan proximate portions of the branches; and (iii) wherein, when in thedeployed configuration, the plurality of branches are in a substantiallyplanar arrangement.
 2. The neurostimulation system of claim 1, wherein,when in the deployed configuration, the plurality of branches are in afan-shaped or rake-shaped arrangement.
 3. The neurostimulation system ofclaim 1, wherein the substantially planar arrangement comprises anarrangement in which the branches branch out across and curve downwardlyfrom a reference plane, wherein the downward curve of the branchesfacilitates maintaining the branches in a subcutaneous tissue layerduring deployment of the electrode array.
 4. The neurostimulation systemof claim 3, wherein at least some of the branches include bluntdissecting distal tips.
 5. The neurostimulation system of claim 1,wherein the non-ablative neurostimulation electrical signals have apulse amplitude of 0-1,000 mA.
 6. The neurostimulation system of claim1, wherein the electrode array further comprises a hub configured to beanchored to a tissue.
 7. The neurostimulation system of claim 1, whereinat least some of the electrode contacts are configured as anodeelectrode contacts and wherein at least some of the electrode contactsare configured as cathode electrode contacts.
 8. The neurostimulationsystem of claim 1, wherein all of the electrodes on one branch areconfigured as anode electrode contacts and wherein all of the electrodeson an adjacent branch are configured as cathode electrode contacts. 9.The neurostimulation system of claim 1, wherein at least some of thebranches include stiffening components configured to increase thestiffness of the branches to facilitate blunt dissecting by thebranches.
 10. The neurostimulation system of claim 9, wherein thestiffening components comprise a plurality of elongate members that areconnected by a stiffening element hub.
 11. The neurostimulation systemof claim 9, wherein at least some of the branches are configured toreceive the stiffening elements.
 12. The neurostimulation system ofclaim 1, wherein the size of the electrode contacts varies as a functionof position on at least some of the branches.
 13. The neurostimulationsystem of claim 12, wherein the branches comprise a proximal end and adistal end, and wherein the size of the electrode contact increases whenthe proximity of the electrode contact to the distal end of the branchincreases.
 14. The neurostimulation system of claim 1, wherein thebranches comprise a proximal end and a distal end.
 15. Theneurostimulation system of claim 14, wherein some of the electrodecontacts are each electrically connected to a resistive element, whereinthe resistance of the resistive element increases when the proximity ofthe electrode contact to the proximal end of the branch increases. 16.The neurostimulation system of claim 1, wherein the pulse generator isconfigured to generate one or more non-ablative neurostimulationelectrical signals.
 17. An implantable electrode array system,comprising: (a) a multi-branch electrode array, the multi-branchelectrode array comprising a plurality of elongated branches extendingalong an insertion axis, wherein each branch includes at least oneelectrode contact and a blunt dissecting distal tip; and (b) animplantation cartridge for deploying the multi-branch electrode arrayfrom a retracted configuration to a deployed configuration, wherein,when in the retracted configuration, the branches are positionedproximally relative to the implantation cartridge, and, wherein, when inthe deployed configuration, the branches extend distally and laterallyoutwardly along a first transverse orientation, relative to theinsertion axis, from the implantation cartridge a further distance thanin the retracted configuration; and wherein, when in the deployedconfiguration, the branches are positioned with a first branch disposedbetween a second branch and a third branch, and a fourth branch disposedbetween the second branch and the first branch so that the electrodearray is distributed along a thin surface.
 18. The implantable electrodearray system of claim 17, wherein at least some of the branches includestiffening components configured to increase the stiffness of thebranches to facilitate blunt dissecting by the branches.
 19. Theimplantable electrode array system of claim 18, wherein the stiffeningcomponents comprise a plurality of elongate members that are connectedby a stiffening element hub.
 20. The implantable electrode array systemof claim 18, wherein at least some of the branches are configured toreceive the stiffening elements.
 21. The implantable electrode arraysystem of claim 18, wherein the stiffening element comprises abiodegradable outer layer on at least some of the branches.
 22. Theimplantable electrode array system of claim 17, wherein at least some ofthe branches include an integrated stiffening element.
 23. Animplantable electrode array, comprising: (a) a multi-branch electrodearray, the multi-branch electrode array comprising a plurality ofelongated branches, wherein each branch includes at least one electrodecontact and a blunt dissecting distal tip; wherein, when in the deployedconfiguration, the branches are arranged in a substantially planarfan-shaped or rake-shaped arrangement.
 24. The implantable electrodearray of claim 23, wherein at least some of the branches includestiffening components configured to increase the stiffness of thebranches to facilitate blunt dissecting by the branches.
 25. Theimplantable electrode array of claim 24, wherein the stiffeningcomponents comprise a plurality of elongate members that are connectedby a stiffening element hub.
 26. The implantable electrode array ofclaim 24, wherein at least some of the branches are configured toreceive the stiffening elements.
 27. The implantable electrode array ofclaim 24, wherein the stiffening element comprises a biodegradable outerlayer on at least some of the branches.
 28. The implantable electrodearray of claim 23, wherein at least some of the branches include anintegrated stiffening element.
 29. A method of implanting aneurostimulation system, comprising: (a) pushing a plurality of branchesof an electrode array into a subcutaneous tissue including or proximatenerve tissue such that distal tips of the plurality of branches piercethrough the subcutaneous tissue and such that the plurality of branchesbranch outwardly into a substantially planar arrangement in which outerbranches on a first side of the electrode array extend away from acenter of the electrode array in a first direction and outer branches ona second side of the electrode array extend away from the center in asecond direction that is opposite the first direction; and (b)connecting the electrode array to a neurostimulation pulse generatorconfigured to stimulate the nerve tissue.
 30. The method of claim 29,further comprising inserting an implantation cartridge through anincision, wherein the implantation cartridge holds the plurality ofbranches of the electrode array.
 31. The method of claim 30, furthercomprising separating the plurality of branches from the implantationcartridge and extracting the implantation cartridge from the incision.32. The method of claim 29, further comprising removing a stiffeningelement from at least one of the branches.
 33. The method of claim 32comprising plugging any void left by the removing of the stiffeningelement from the at least one of the branches.